I think you are doing fine. That's fine since paph and phals are not heavy feeders.
I didn't fertilize for three months (oops, I was consumed with starting up my reef tank) and my plants are fine. My plants are getting into sheath and spike now, and some unexpected seedlings too suprisingly. I used to (or tried to) do weekly weekly though, but I am not sure if it changed anything. When I did weakly weekly, yes the amount was reduced or there would be too much salt in the water, which would eventually build up.
Interestingly I overheard a vendor talking to a customer this year's orchid show and the vendor said "no don't do weakly weekly, you are over fertilizing. Just fertilize every month." Obviously they were discussing a problem of some sort but I don't know what. How I am interpreting this comment is that the plants get stimulated by a sudden rush of nutrients.
What I do recommend is finding a urea (nitrogen compound) free fertilizer. Many fertilizers are urea based and this compound needs to be further broken down by microrganisms (which are not as abunant in bark) before it can be absorbed. Nitrate and Nitrites can be absorbed readily to stimulate leaf growth
I just did some fertilizing today, and did repotting (but not finished). The plants are all going into active growth as daylength is increasing! What is odd though is that my underlight plants who see no sun at all seem to detect spring...something to think about